Magnetoelectric Effect in Garnet Mn₃Al₂Ge₃O₁₂

Abstract

Searching for novel magnetoelectric (ME) materials has been one of the major issues of multiferroics. In this work, we present a systematic research study on garnet Mn 3 Al 2 Ge 3 O 12 , including structural, magnetic, heat capacity, and ME characterizations. Below the Neél temperature T N ∼ 6.8 K, Mn 2+ spins form a long-range antiferromagnetic order, and a magnetic field Hdriven electric polarization P is identified simultaneously. The relationship between P and H is nonlinear under low H and becomes linear under high H. Such transition is believed to originate from the H-induced variation of the magnetic structure. In addition, the P reaches 0.6 μC/m 2 under μ 0 H = 9 T, corresponding to an ME coupling coefficient of α ME ∼ 0.08 ps/m under high H. The small α ME is attributed to the weak spin−orbit coupling and weak magnetic interactions in Mn 3 Al 2 Ge 3 O 12 . Furthermore, we realize the stable control of P by periodically varying H, which is crucial for potential application. We provide a rare case that a garnet material shows a first-order ME effect.

Frustrated Magnet Mn3Al2Ge3O12 Garnet: Crystal Growth by the Optical Floating Zone Method

“…Profile matching confirms that the main phase is the Mn 3 Al 2 Ge 3 O 12 cubic garnet phase, with no significant impurity phases present. The lattice parameter was determined to be a = 11.90479(5) Å, in agreement with previous studies [20].…”

“…This was in agreement with further studies of the magnetic properties and specific heat measurements by Valyanska et al [19]. Mn 3 Al 2 Ge 3 O 12 has also recently been shown to display the first order magnetoelectric effect, which is rare for a garnet and is promising for future applications [20].…”